I know nothing about this. Marcel Boeuf also patented a straight-forward looking twin pulley derailleur in 1927, but I have never seen or heard anything else about him or is mechanisms.

• Publisher: L’Institut national de la propriété industrielle
• Inventor: Marcel Boeuf
• Country: France
• Date: French application May 1931
• Derailleur brands: Phénix
• Derailleurs: unknown